Abstract

The N-type untwinning surface relief associated with the fcc ↔ fct martensitic transformation (MT) was observed in the Mn81.5Fe14.0Cu4.5 antiferromagnetic high-temperature shape memoryalloy (SMA) by in situatomic force microscopy. The measured untwinning relief angles (θα|θβ) at the ridge and at the valley were different, and both angles were less than the conventional values. The surface relief exhibited good reversibility during heating and cooling because of the crystallographic reversibility of thermal-elastic SMAs. Untwinning shear was proposed as the main mechanism of the N-type surface relief. The order of the reverse MT was discussed based on the experimental measurements.